Simulator - Lesson 4

Hey There!I am currently in lesson 4 in this catagory and i have a problem. When I want to simulate the simple app it open the window with the Nexus 5 device and black screen with a "android" in the middle like you open an android phone and stuck right there. It is show me that for a 15 min and not start the device and the app. Can someone help me please?